Purge on colour change: the plastic that gets thrown away

Why purging is needed

After one colour is printed, the nozzle still holds molten plastic of the old colour. If it carried on straight into the part, an unwanted streak of mixed colour would show up. So after each filament change a certain amount is pushed out onto the wipe tower, and only then does the nozzle go back to printing. The settings are described on the OrcaSlicer wiki.

What decides the amount

• Colour combination. Going from dark to light needs the most purge, light to dark much less.
• Number of changes. Every change adds another purge, so the amounts add up.
• Part size. On small parts the purge often ends up bigger than the part itself.

How to reduce purge

The most effective thing is to cut the number of colour changes over the height of the part. A well-planned design has colours in long blocks and few transitions, for example a two-colour base and lid instead of stripes. What matters is not only how many colours you use, but how many times they have to be swapped. See multicolour printing.

Purge on a single part and in a batch. On one small part the purge is relatively the biggest, because it has to happen after every colour change no matter how big the part is. In a batch the purge is shared, so less falls on each part.

Purge on your order

For multicolour parts the purge is included in the price per part and is not a separate line. If you want a lower price, send a 3MF with as few colours and colour changes as possible.